The present invention relates to heat-sensitive record materials, such as recording media for facsimile printers. In particular, a double-surface heat-sensitive record material is disclosed for use in generating at least two separable printed surfaces, such as a label and a receipt.
Heat-sensitive record materials generate colored images by thermally bringing a color-forming material into contact with a color-developing material. A recording apparatus is utilized to apply thermal energy in the shape of the desired image. Typical recording printers are found in facsimile machines, cash registers, and measuring instruments. Heat-sensitive record materials have gained widespread popularity, because of the ease of maintenance of the recording apparatuses, which do not require ink transfer materials (e.g., an ink ribbon or tape) and typically utilize virtually no moving parts to transfer the thermal energy to the record material. Relatively thick, heat-sensitive record materials have recently been used as durable product labels, that display machine-readable "bar-code" information, and human-readable, traditional letters and/or numbers.
Heat-sensitive record material is produced by applying a heat-sensitive coating composition to a base support sheet via conventional paper coating procedures. Once heat-sensitive record material is prepared by such a process, subsequent processing is severely limited because the material is thereafter subject to deleterious discoloring when exposed to heat levels associated with ordinary paper processing. Consequently, the variety of heat-sensitive record materials available has been limited.
For example, a common label that utilizes a heat-sensitive record layer is widely utilized in package delivery. First, the label has information thermally imaged or printed onto the heat-sensitive record layer by a hand-held recording apparatus, typically operated by an individual picking up the package for delivery. The label then has a release liner peeled away from a surface opposed to the information-bearing, heat-sensitive record layer, thereby exposing a pressure-sensitive adhesive layer. The label is then affixed to the package, and the release liner is discarded.
In producing such a label, a heat-sensitive composition is applied to a first base support sheet. Then a second support sheet or release liner is coated with a pressure-sensitive adhesive, and the two support sheets are laminated together by a cold lamination process, such as press rolling, to form the label material.
To avoid duplicative clerical work and inefficient disposal of the release liner after application of the label to the package, it is desirable to further process the label material, by, for example, applying another layer of heat-sensitive coating compound to the release liner, so that the release liner could be simultaneously printed to produce a receipt. Further processing, however, has so far proven impractical for two primary reasons. First, coating a second heat-sensitive record layer directly to the release liner side of the label material at an efficient manufacturing, or "line", speed necessarily involves exposure of the previously applied, or first, heat-sensitive record layer to levels of heat and chemicals that cause the first layer to prematurely color, or develop a fogginess, rendering the product unusable. Second, coating a second heat-sensitive record layer directly onto the release layer side of the label material at an efficient line speed is not technically feasible because the thickness or bulk of the label material renders requisite uniform coating of the heat-sensitive coating composition impossible.
Accordingly, it is the general object of the present invention to provide a double-surface heat-sensitive record material that overcomes the problems of the prior art.
It is a more specific object to provide a double-surface heat-sensitive record material which enables simultaneous thermal imaging or printing of two separable opposed surfaces.
It is another specific object to provide a double-surface heat-sensitive record material which can be produced at efficient manufacturing or line speeds.
It is yet another specific object to provide a double-surface heat-sensitive record material which can be produced without discoloration of any of the heat-sensitive record material.
The above and other objects and advantages of this invention will become more readily apparent when the following description is read in conjunction with the accompanying drawings.